The proposed research is to develop thiol-ene polymers for application as dental restorative materials. The goals of this research are to develop thiol-ene materials that will have superior properties relative to current polymers utilized for dental restorative materials. The research will involve studying the relationship between chemical structure, polymerization kinetics, and material properties, these studies will be conducted with commercially available monomers and also novel thiol and ene monomers synthesized in the Bowman and Stansbury research groups. Thiol-ene based dental composite systems with filler particles will also be studied. Critical areas that will be addressed are volume shrinkage and shrinkage stress as well as the stability of the monomer formulations. The compatibility of monomer formulations with filler particles and the properties of filled systems will be evaluated. Biocompatibility of the new dental restorative materials will also be assessed.